Multi-position switch with improved wafer switch contact arrangement

ABSTRACT

A multi-position switch for a decade resistor capable of changing the resistance between a pair of terminals monotonically from 0 to 9 units in ten equal steps in one direction and back to 0 in the eleventh step in the same direction. One resistor of unit resistance value is connected in series with four resistors of 2-unit resistance value between the terminals, and the switch contacts are arranged so that the terminals are shorted together in a first position and in each successive position the unit value resistance is alternately included in series between the terminals or short-circuited and replaced by an additional 2-unit resistor.

United States Patent 1191 Runtz [75] Inventor:

[73] Assignee: North American Philips Corporation, New York, NY.

22 Filed: Aug. 10,1971

21 Appl.No.: 170,521

Jean W. Runtz, Morton Grove, Ill.

1451 May 1, 1973 Williams ..200/ l l D X Primary Examiner-J. R. Scott Attorney-Frank R. Trifari 5 7 ABSTRACT A multi-position switch for a decade resistor capable 52 us. 01. ..200/11 D, 200/156 of Changing the resistance between a p of terminals 51 1m. (:1 .110111 19/58 monotonically from 0 to 9 units in ten equal steps in [58] Field of Search ..200/11 D, 1 1 DA, one direction n back to 0 in he eleven h tep in the 200/156 same direction. One resistor of unit resistance value is connected in series with four resistors of 2-unit re- [56] References Cited sistance value between the terminals, and the switch contacts are arranged so that the terminals are shorted UNITED STATES PATENTS together in a first position and in each successive posi- 3,303,311 2/1967 Strever ..200/l56 tion the unit value resistance is alternately included in 2,594,190 4/1952 Mastney ....200/1 1 D series between the terminals or short-circuited and 2,190,301 2/1940 Vernam et a]. ....200/ll D replaced by an additional 2-unit resistor. 3,248,488 4/1966 Stephan ..20()/ll D 2,976,384 3/1961 Winston .200/1 1 D X 11 Claims, 7 Drawing Figures (I2 I I l 5 I4 I 6 l3 o o 31 43 500 IT 0 2 I 36 I8 7 4 lOb Patented May 1, 1973 3,731,017

I 2 Shets-Sheet 1 FIGS +2 INVENTOR. JEAN W. RUNTZ ATTORNEYS Patented May 1, 1973 2 Sheets-Sheet FIG. 7

INVENTOR. J'EAN W. RUNTZ ATTORNEYS MULTI-POSITION SWITCH WITH IMPROVED WAFER SWITCH CONTACT ARRANGEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to decade resistors and to the switch arrangement therefor. In particular, it relates to a simplified decade resistor and switch structure capa- 10 ble of varying the resistance and unit value steps between and 9 and back to 0 in a total of 11 steps in one direction and of being able to progress through that series by actuating a switch repeatedly as many times as may be desired, either in one direction for increasing the resistance from step to step or in the other direction that a total of nine resistors of unit value is required to obtain nine units of resistance or else all of the resistors have different values, such as l, 2, 3, and 4 units. Resistor boxes in which all of the resistors have the same value have a relatively simple switching structure, at least in going in one direction from 0 to 9 units and then steping back unit by unit to 0, but they are expensive, at least in the requirement for nine precision resistors. Decade resistors in which all of the resistance units have different resistance values do not need as many precision resistors, but the complexity of the switching structure itself is increased. Many decade resistors do not permit the sequence of values to be obtained repeatedly by turning the control knob in one direction. Instead, such decade resistors have means to limit the rotation of the control knob to less than 360.

It is one of the objects of the present invention to provide a decade resistor of simple construction and one which uses a minimum number of precision resistors to obtain any value of resistance from 0 to 9 units.

Another object of the invention is to provide a switch mechanism of simple construction for use in decade resistors.

A further object is to provide a decade resistor switch in which the control can be actuated as many times as may be desired in one direction to cause the resistance to vary repeatedly from 0 to 9 units in ten steps and to start over again at 0 on the next step, or to change in the reverse order by moving the control in the opposite direction.

Further objects will be apparent from the following specification and drawings.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, a decade resistor is formed of five precision resistors, one of which has a value of one unit of resistance, each of the other four resistors having a value of two units of resistance. A typical unit would be a power of 10, such as ohms, 100 ohms, 1 000 ohms, etc., but other values may be used if desired. The resistors are connected to a switching device that comprises two groups of contacts movable relative to the otherQFor example, one group may be arranged in a circle on a rotatable member and another group in a concentric circle on a fixed member so that the contacts on the rotatable member can selectively engage the fixed contacts as the rotatable member turns. Normally the resistors would be attached to the fixed member.

More specifically, the movable group of contacts of the switching device is divided into two similar units with the contacts in each of the units spaced equal incremental distances apart along a direction which is the relative direction of motion between the fixed group and the movable group. In the case of rotatable contacts, the direction is tangential to the circle on which contacts are located. Each of the two units is divided into an equal number of long contacts and short contacts placed alternately so that there is a long contact at one end of each unit and a short contact at the other. All of the contacts in each unit are short-circuited together, but the units are insulated from each other. The long contact adjacent the end short contact is extra long to engage all contacts of the other group.

The other group is composed of a third contact unit having the same number of contacts as each of the first and second units. The contacts in the third unit are spaced apart along the above-mentioned direction by the same incremental distance as the distance between neighboring contacts of either the first unit or the second unit. The third unit comprises two end contacts that extend farther toward the contacts of the first and second units than any of the other contacts in the third unit. As a result, these two end contacts can engage any of the contacts of the first and second units. Adjacent one of the end contacts of the third unit is a somewhat shorter contact that can engage any of the longer contacts of either the first or the second unit but cannot engage the short contacts of the first or second unit. Finally, between the last-mentioned contact of intermediate length and the other long contact of the third unit is a series of short contacts capable of engaging only the extra long contact of the first and second units. In a decade resistor utilizing this switching device there are seven short contacts in the third unit and five short and five long contacts in each of the first and second units.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of one deck of a decade resistor switch constructed according to the present invention.

FIG. 2 shows the reverse side of the switch of FIG. 1.

FIG. 3 is a front view of a multi-digit switch comprising several sections of the switch of FIGS. 1 and 2.

FIGS. 4-7 are schematic arrangements of a decade resistor and switch according to the invention.

DETAILED DESCRIPTION OF THE INVENTION The decade resistor 10 in FIG. 1 comprises a plastic housing 11 for the actuating mechanism of the switch. The housing is closed at one side by an insulating panel 12 on which are mounted a group of stationary contacts 13 arranged as an arcuate unit. These contacts are all pointed substantially radially inwardly. They include a first long contact 14, a contact 15 of lesser length than the contact 14 seven shorter contacts 16-22, and another long contact 23 of the same length as the contact 14. Each of the contacts 14-23 is equally angularly displaced from its neighboring contacts, and the total included angle between the contact 14 at one end of the group and the contact 23 at the other end is 162. Thus the angular spacing between any adjacent pair of these contacts 14-23 is 18. All of the contacts 14-23 are mounted on an arcuate section 24 of the insulating plate 12.

In addition to the fixed contacts 14-23, there is a group of movable contacts 26 divided into two units. One of these is the unit 27 and the other is the unit 28, and both units are mounted on a rotatable insulating member 29. All of the contacts in the unit 27 are electrically short-circuited together as are the contacts of unit 28, but the contacts of units 27 and 28 are separated from each other by gaps 31 and 32. These gaps are relatively short so that each of the contacts, or more precisely, contact areas, are equally spaced from each other. The two units 27 and 28 are symmetrical with respect to each other about the center of the disc 29.

Since the contacts of the unit 27 are somewhat obscured by the stationary contacts 14-23, the contacts of unit 28 will be described in detail. These include five contacts 33-37 that extend radially outwardly a shorter distance than the remaining contacts of the unit 28. As may be seen, the radial dimension of these contacts is such that they would only make connection with the longest contacts 14 and 23 of the stationary group of contacts 13. The relatively radially short contacts 33-37 are interleaved with relatively longer (in a radial direction) contacts 39-43 of which the contact 39 is longer than the rest and is capable of making connection with the shortest stationary contacts 16-22. Contact 39 is, of course, also capable of making connection with the intermediate length contact 15 and the long contacts 14 and 23. The remaining long contacts 40-43 are radially shorter than the contact 39 but longer than the contacts 33-37. These contacts 40-43 may be considered to be of intermediate length and are capable of connecting with the intermediate length stationary contact 15 as well as the long contacts 14 and 23 but not with the shorter contacts 16-22.

As shown in FIG. 2, a group of resistors 44-48 is connected in series with each other and the junctions between these resistors as well as the two end terminals of the series circuit are connected to selected terminals and pairs of terminals of the contacts 14-23. The resistor 44 has a unit value resistance and the other resistors 45-48 all have resistances of two units. Typical values of the unit value would be in powers of 10, for example, ohms, 100 ohms, 1,000 ohms, etc., but it is not necessary that the units be in powers of 10. It is perfectly permissible for the unit value to be some other value entirely, but the relationship of one unit value of resistance for the resistor 44 and two units for each of the remaining resistors must be maintained if the total resistance is to be divided by nine.

As may be seen, one terminal of the resistor 44 is connected directly to the long end contact 14 and the other terminal of the same resistor is connected to the contact 15. This contact is also short-circuited directly to the contact 16. One end of the second resistor 45 is connected to this short-circuited pair of contacts and 16 and the other terminal is connected to the contact 17, which is short-circuited to the contact 18. The resistor 46 is connected at one end to the terminals 17 and 18 and at the other to the terminals 19 and 20, which are short-circuited together. The resistor 47 has one of its terminals connected to the short-circuited contacts 19 and 20 and the other terminal connected to another short-circuited pair of contacts 21 and 22. The last resistor in the series circuit is the resistor 48 and one of its terminals is connected to the pair of contacts 21 and 22 short-circuited together. The other terminal of the resistor 48 is connected directly to the end contact 23.

The switching mechanism in the decade resistor 10 is not a part of the present invention and therefore the internal components of the switch need not be described. Externally the decade resistor has an actuator that consists of two members 50 and 51 which have roughened pressure surfaces and are intended to be depressed by finger action. when the member 50 is repeatedly depressed without depressing the member 51, the internal mechanism of this known switch causes the disc 29, to which the movable contacts are attached, to rotate 18 in one direction for each actuation of the member 50. Conversely, if the member 51 is repeatedly depressed, it will cause the disc 29 to rotate in the reverse direction 18 each step.

FIG. 3 shows a group of decade resistors 10, 10a, and 10b mechanically connected together side by side. As may be seen, each of the decade resistors is provided with indicating digits in the center between the pressure members 50-50b and 51-51b. These indicating digits are identified by reference numerals 525%, and, in accordance with standard decade numbering, switch 10 would have a basic unit value resistance, such as 1 ohm, the decade resistor 10a would have a basic resistance value 10 times as high as the basic resistance value of the switch 10, and the switch 10b would have a basic value 10 times as high as the basic value of the switch 10a. Thus, the relationship of the three decade resistors 10-10b corresponds to ordinary 3-digit decade notation. It should be noted that the three decade resistors 50-50b are connected in series with each other to provide any resistance value from zero to 999N where N is the unit value of resistance in the decade resistor 10.

In order to describe more clearly the stepping operation of the decade resistor, the three contact units 13, 27, and 28 are shown in FIGS. 4-7 stretched out flat. The individual contacts in the unit 27 are identified by reference numerals that correspond to those in the contact unit 28 with the addition of the suffix a.

The relative position between the contact units in FIG. 4 is such that there is zero resistance between the end contacts 14 and 23, which are also the terminals of the decade resistor. This is caused by the fact that both of the contacts 14 and 23 connect with the unit 27 and thus are short-circuited by the unit 27 More specifically, the contact 14 connects with the contact 33a while the contact 23 connects with the contact 430 at the other end of the unit 27. The contact 15 connects with the contact 39a of the unit 27 in this position so that the resistor 44 is separately short-circuited. However, this is immaterial since the connection from the contact 14 through the unit 27 to the contact 23 shortcircuits all of the resistors 44-48.

FIG. 5 shows the relative position of the contact units 13, 27, and 28 to achieve a resistance value of three units between the end contacts 14 and 23. This resistance value is obtained by moving the units 27 and 28 three steps to the right relative to the unit 13. In this position, the contact 14 connects with the contact 42 while the contact 23 connects with the contact 360 and the contact 18 connects with the contact 39a. Since the contact 39a and the contact 36a are both part of the unit 27 and are short-circuited together, the resistors 46-48 are short-circuited. The resistors 44 and 45 form the only active parts of the series circuit between the contacts 14 and 23. The resistor 44 has one unit of resistance and the resistor 45 has two units of resistance, making a total of three units of resistance between the contacts 14 and 23.

The relative position of the contact units in FIG. 6 produces a resistance value of six units between the contacts 14 and 23. In this case, the contact 14 is in connection with the contact 35 and the contact 15 is in connection with the contact 41, thus short-circuiting the unit value resistance of the resistor 44. The contact 21 is in connection with the contact 39a and the contact 23 is in the connection with the contact 40a, thus short-circuiting the resistor 48. The resistors that remain active in the series circuit are resistors 45-47, and each of these has a resistance value of two units, making a total of six units of resistance between the contacts 14 and 23.

By comparison of FIGS. 5 and 6, it may be seen that each time the contact units 27 and 28 are moved one step to the right relative to the contact unit 13, the resistor 44 is either short-circuited or is added to the active group of resistors. If it is added to the group of resistors, it obviously increases the resistance by one unit. On the other hand, if it is short-circuited it is subtracted but is replaced in the active group of resistors by a resistor of two units of resistance value so that there is a net increment of one unit of resistance. Obviously moving the contact units 27 and 28 to the left relative to the contact unit 13 reduces the resistance between the contacts 14 and 23 one unit for each step.

FIG. 7 shows the relative position of the contact units 13, 27, and 28 when all of the resistors 44-48 are active. In this position, the contact 14 is in connection with the contact 39 and the contact 23 is in connection with the contact 33a. None of the other contacts are in connection, and, therefore, none of the resistors 44-48 is short-circuited.

What is claimed is:

1. In a switching device for providing sequential resistance values of the type having means to advance one set of contacts relative to another set of contacts, an improved contact arrangement comprising:

a first electrically conductive plate having commencing and terminating ends and having a plurality of transverse contact projections extending from one side of said plate, said projections being substantially of equal width and being spaced apart, all of said projections being of equal length with the exception of one projection, the length of which is greater than said equal projections, said longer projection being closest to said terminating end of said plate, all of said projections and said plate being electrically interconnected;

a second electrically conductive plate having a commencing end and terminating end of substantially identical construction as said first plate, said second plate electrically isolated from said first plate and positioned so that the commencing end of said second plate is juxtaposed to the terminating end of said first plate;

contact member having a plurality of individual contacts, each individual contact corresponding to a projection or space between projections of one of said plates, said contact member having relatively long commencing and terminating end contacts, said commencing contact being positioned opposite said commencing end of said first plate in an initial position, said terminating contact being positioned opposite said terminating end of said first plate in said initial position, 'said contact member also having relatively short substantially equal length contacts between said end contacts with the exception of one contact adjacent said terminating contact which is of relatively intermediate length, said contact member being positioned so that commencing and terminating contacts extend to at least the depth of spaces between projections of said first or second plates and make electrical contact with said plate, said intermediate length contact extending at least to the ends of said equal length projections but not to the depth of spaces between projections and adapted to making electrical contact with said projections, and said short contacts extending to at least the end of said longer projection but not to the ends of said equal projections, said short contacts adapted to making electrical contact only with said longer projection, said contact member and said plates being mounted for relative movement whereby said advancing means causes said contacts of said contact member to advance relative to said initial position toward said second plate.

2. The contact arrangement of claim 1 wherein said first and second plates each have four equal length projections and one longer projection, the commencing end of each plate having one of the equal length projections extending therefrom, each of said equal projections being separated by a space approximately equal to the width of a projection, said spaces being of approximately equal depth, said plates having a main section from which said projections extend, said main section extending past said longer projection of said terminating end the approximate width of one projection.

3. The contact arrangement of claim 1 wherein said contact member has 10 individual contacts, comprising said commencing contact, a second small contact adjacent said commencing contact, a third small contact adjacent said second contact, a fourth small contact adjacent said third contact, a fifth small contact adjacent said fourth contact, a sixth small contact adjacent said fifth contact, a seventh small contact adjacent said sixth contact, an eighth small contact adjacent said seventh contact, said intermediate contact adjacent said eighth contact and said terminating contact adjacent said intermediate contact.

4. A sequential resistance switching circuit in combination with the contact arrangement of claim 3 wherein a first resistance element is electrically connected between said commencing contact and said second contact, a second resistance element is connected between said third and fourth contact, a third resistance element is connected between said fifth and sixth contact, a fourth resistance element is connected between said seventh and eighth contact, and a fifth resistance element is connected between intermediate and terminating contacts, and wherein said second and third contacts are directly connected, said fourth and fifth contacts are directly connected, said sixth and seventh contacts are directly connected and said eighth and intermediate contacts are directly connected, wherein a predetermined sequence of resistance values are effected between said commencing and terminating contacts of said contact member by the relative advancement of said contact member with respect to said first and second plates.

5. The contact arrangement of claim 4 wherein said first, second, third and fourth resistor are equal and are of twice the value of said fifth resistor.

6. The contact arrangement of claim 5 wherein said first, second, third, and fourth resistor are an integral power of 10 including zero.

7. The arrangement of claim 1 wherein said contact member is physically fixed and said plates move relative to said contact member.

8. The arrangement of claim 1 wherein said plates are fixed and said contact member moves relative to said plates.

9. The arrangement of claim 1 wherein said plates 

1. In a switching device for providing sequential resistance values of the type having means to advance one set of contacts relative to another set of contacts, an improved contact arrangement comprising: a first electrically conductive plate having commencing and terminating ends and having a plurality of transverse contact projections extending from one side of said plate, said projections being substantially of equal width and being spaced apart, all of said projections being of equal length with the exception of one projection, the length of which is greater than said equal projections, said longer projection being closest to said terminating end of said plate, all of said projections and said plate being electrically interconnected; a second electrically conductive plate having a commencing end and terminating end of substantially identical construction as said first plate, said second plate electrically isolated from said first plate and positioned so that the commencing end of said second plate is juxtaposed to the terminating end of said first plate; a contact member having a plurality of individual contacts, each individual contact corresponding to a projection or space between projections of one of said plates, said contact member having relatively long commencing and terminating end contacts, said commencing contact being positioned opposite said commencing end of said first plate in an initial position, said terminating contact being positioned opposite said terminating end of said first plate in said initial position, said contact member also having relatively short substantially equal length contacts between said end contacts with the exception of one contact adjacent said terminating contact which is of relatively intermediate length, said contact member being positioned so that commencing and terminating contacts extend to at least the depth of spaces between projections of said first or second plates and make electrical contact with said plate, said intermediate length contact extending at least to the ends of said equal length projections but not to the depth of spaces between projections and adapted to making electrical contact with saId projections, and said short contacts extending to at least the end of said longer projection but not to the ends of said equal projections, said short contacts adapted to making electrical contact only with said longer projection, said contact member and said plates being mounted for relative movement whereby said advancing means causes said contacts of said contact member to advance relative to said initial position toward said second plate.
 2. The contact arrangement of claim 1 wherein said first and second plates each have four equal length projections and one longer projection, the commencing end of each plate having one of the equal length projections extending therefrom, each of said equal projections being separated by a space approximately equal to the width of a projection, said spaces being of approximately equal depth, said plates having a main section from which said projections extend, said main section extending past said longer projection of said terminating end the approximate width of one projection.
 3. The contact arrangement of claim 1 wherein said contact member has 10 individual contacts, comprising said commencing contact, a second small contact adjacent said commencing contact, a third small contact adjacent said second contact, a fourth small contact adjacent said third contact, a fifth small contact adjacent said fourth contact, a sixth small contact adjacent said fifth contact, a seventh small contact adjacent said sixth contact, an eighth small contact adjacent said seventh contact, said intermediate contact adjacent said eighth contact and said terminating contact adjacent said intermediate contact.
 4. A sequential resistance switching circuit in combination with the contact arrangement of claim 3 wherein a first resistance element is electrically connected between said commencing contact and said second contact, a second resistance element is connected between said third and fourth contact, a third resistance element is connected between said fifth and sixth contact, a fourth resistance element is connected between said seventh and eighth contact, and a fifth resistance element is connected between intermediate and terminating contacts, and wherein said second and third contacts are directly connected, said fourth and fifth contacts are directly connected, said sixth and seventh contacts are directly connected and said eighth and intermediate contacts are directly connected, wherein a predetermined sequence of resistance values are effected between said commencing and terminating contacts of said contact member by the relative advancement of said contact member with respect to said first and second plates.
 5. The contact arrangement of claim 4 wherein said first, second, third and fourth resistor are equal and are of twice the value of said fifth resistor.
 6. The contact arrangement of claim 5 wherein said first, second, third, and fourth resistor are an integral power of 10 including zero.
 7. The arrangement of claim 1 wherein said contact member is physically fixed and said plates move relative to said contact member.
 8. The arrangement of claim 1 wherein said plates are fixed and said contact member moves relative to said plates.
 9. The arrangement of claim 1 wherein said plates are arranged circularly so that said terminating end of said second plate is juxtaposed to said commencing end of said first plate.
 10. The arrangement of claim 1 wherein said contact member is arranged on a portion of a circle.
 11. The arrangement of claim 1 wherein said contact member is arranged as a partly annular outer element, said contacts being inwardly radially directed and said plates being arranged as a circular inner element. 